1. Field of the Invention
This invention is in the field of attenuators or mufflers, or more specifically, insert type attenuators designed to smooth out pulsations, that is, fluctuations in pressure and flow, in a liquid or liquid suspension such as one being fed to a paper making headbox, and providing a sensitive, automatically balanced system including a flexible diaphragm responsive to fluctuations in the pressure of the stock suspension on one side and cushioned by and positioned by an automatically controlled gas pressure on the other side.
2. Description of the Prior Art
In stock lines feeding paper machines, it is highly desirable that the fluid be delivered at a steady rate. In the case of a paper machine stock system, pulsations in the stock suspension which might be caused by pumps or screens or the like or by disturbances such as cavitation may lead to "barring" of the paper being produced. This defect, variations in the area density of the paper in the machine direction, is accompanied by or causes other problems both in manufacturing and in using the paper.
Several approaches have been tried to solve the problem of basis weight or wet-end barring. One approach is to reduce the magnitude of fluctuations contributed by sources such as pumps and screens. Selection, redesign, and more strict tolerances in manufacture and in field installation as well as attention to fluid dynamics are of some help in achieving reduction. A more universal approach is the use of a properly designed and properly applied attenuator or acoustic filter which should reduce the magnitude of the undersired fluctuating or ac components of the flow significantly without significantly interfering with the steady or dc component of flow.
A theoretical and practical discussion of basis weight barring, and the governing principles of attenuation using filters of the reactive type will be found in my two papers published in Volume 60, No. 10 of "Tappi" (October 1977), and in the succeeding issue, Volume 60, No. 11 (November 1977).